Open interest vs volume in options
The short answerVolume counts the option contracts traded during the day; open interest counts the contracts still open at the end of it. Volume starts from zero each morning. Open interest carries over: it rises when new positions are opened, falls when positions are closed, and is counted once a day, overnight.
How a trade changes open interest
| Trade | Volume | Open interest |
|---|
| A buys 1 new call from B, who opens a short | +1 | +1 (a new contract exists) |
| A sells that call to C | +1 | no change (the contract changed hands) |
| C sells it back to B, who closes the short | +1 | −1 (the contract is gone) |
Three trades, volume 3 — and open interest back to where it started.
Reading the two together
- High volume and open interest rising: new positions are being built — the move has fresh money behind it.
- High volume and open interest falling: positions are being closed — often profit-taking or covering.
- Volume far above open interest at a strike: unusual activity — someone traded more contracts than existed the day before.
Why open interest drives the levels
Max pain, the walls and gamma exposure are all built from open interest, because it is what remains to be hedged overnight. Open interest is published by the clearing house before the next open, so the figure shown with a session’s chain describes the positions at the close before.
Live example: SPY and QQQ today
From the close of Fri, Nov 13, 2026 — this box is rebuilt after every trading day.
SPY on Nov 13, 2026:
| Calls | Puts |
|---|
| Open interest | 6,061,214 | 11,209,829 |
| Volume | 5,608,422 | 6,731,856 |
Open interest changed by −662,898 contracts from the session before. Volume was 0.99× its 20-session average. Open interest and volume by strike: SPY (strike table download).
Questions and answers
Is high open interest bullish?
No — every open contract has a buyer and a seller. High open interest means many positions are open at that strike, which matters for hedging and for levels like the walls, not for direction by itself.
When is open interest updated?
Once a day. The clearing house counts it overnight, so it is the same all day long, while volume updates with every trade.
Can volume be higher than open interest?
Yes. Contracts can be bought and sold many times in a day, and positions opened and closed the same day add to volume but never to open interest.
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